Sitecore Identity was introduced in Sitecore 9.1 and uses the new Federated Authentication functionality. By using the same techniques as Sitecore Identity it's possible to implement a custom identity provider.
By using the Hybrid Placeholder it's possible to use asynchronous loading for heavy parts of a custom Rendering Contents Resolver.
With the contract-first workflow the frontend and backend developers can work in parallel based on a data structure 'contact'.
This blog will explain how you can have more control over the generated files.